Our invention relates generally to an apparatus having a data transducer or transducers driven by an electric seek motor for accessing any of a multiplicity of concentric annular record tracks on a rotating disklike record medium such as a flexible magnetic disk which may be packaged in cassette or cartridge form. More specifically, our invention deals with a method of, and means for, saving power in such a rotating disk data storage apparatus by holding the seek motor unenergized when the data transducer or transducers are not in track seek operation.
Generally, in rotating disk data storage apparatus of the type under consideration, the seek motor takes the form of either a voice coil motor or a stepper motor. Our invention particularly concerns apparatus of the class employing the stepper motor for causing the data transducer or transducers to move to any desired tracks on the disk or disks.
The stepper motor has a rotor that rotates in short and essentially uniform angular movements, rather than continuously, in response to stepping pulses supplied from a host system external to the data storage apparatus. The stepwise rotation of the stepper motor is converted by a motion translating mechanism into the linear stepwise travel of the transducer or transducers for track to track accessing on the disk or disks. There are, here again, two familiar examples of the motion translating mechanism: one employs a lead screw, and the other a steel belt. An example of steel belt type motion translating mechanism is described and claimed in U.S. Pat. No. 4,774,611 filed by Ando and assigned to the assignee of the instant application.
The stepper motor need not be held energized throughout each period of operation of the data storage apparatus as the motor is used only for moving the transducer or transducers from track to track on the disk or disks. The continued energization of the stepper motor would involve a substantial waste of energy. It has therefore been suggested to hold the stepper motor unenergized when the transducer or transducers are out of seek operation. U.S. Pat. No. 4,783,706 filed by Shoji et al. and assigned to the assignee of our present application describes and claims such a power saving method and electronics for implementing the method.
We have found that the noted Shoji et al. U.S. patent has a drawback when the stepper motor is used in combination with the steel belt motion translating mechanism. The drawback arises because of the smaller detent torque exerted by the steel belt on the stepper motor than by the lead screw when the motor is disconnected from the power supply. Consequently, in event mechanical vibrations or shocks are applied to the stepper motor when it is unenergized, the rotor of the stepper has been very liable to be displaced with respect to the fixed motor windings, being no longer electromagnetically retained in the required angular position. Thus the transducer or transducers coupled to the rotor via the steel belt motion translating mechanism have been easy to be displaced from the required track positions on the disk or disks.